Question

Упростите выражение: $( frac{sin x}{tg x})^{2} + ( frac{cos x}{ctg x} )^{2} - 2 sin^{2}x$

Answer 1

$frac{sin^2x}{ frac{sin^2x}{cos^2x} }+ frac{cos^2x}{ frac{cos^2x}{sin^2x} }-2sin^2x=cos^2x+sin^2x-2sin^2x=1-2sin^2x=cos2x$